Contact seals, often made of carbon and hence referred to correctly or incorrectly as carbon seals, are commonly used to provide a fluid seal around a rotating shaft, particularly high speed rotating shafts used in high temperature environments such as in gas turbine engines. Such contact seals usually comprise ring segments and a runner which abut and rotate relative to each other to form a rubbing, contact interface which creates a fluid seal around the shaft. Pressurized gas can be used to force the ring segments against the seal runner and create a gas pressure differential with the bearing cavity which repels impinging oil. Typically, but not necessarily, the seal runner is disposed on the rotating shaft and rotates within an outer stationary ring, causing the rubbing interface between the rotating seal runner and the rotationally-stationary ring. Although efforts are made to limit friction, the rubbing contact can generate significant heat during operation, especially in the context of high rotational speeds of gas turbine engine shafts, and means are provided to dissipate this heat. This heat dissipation is most often accomplished using fluid cooling, for example oil from the engine's recirculating oil system which is sprayed onto exposed surfaces of the seal runner and/or the ring.
It was known to provide seal runners which were internally cooled. Publication US 2014-0369832, in particular, discloses a runner assembly having a plurality of independent, circumferentially interspaced, tortuous internal cooling fluid conduits along which cooling fluid was conveyed to cool the radially-inner surface of the seal runner. While this runner assembly had a relatively small radial thickness, which was particularly sought in the context, the cooling fluid passages terminated in outlet apertures.
Accordingly, there always remains room for improvement.